IIRC, In the US at least (I assume similar laws exist in other countries), the minute you put a packet "or in other words, any encapsulated form of data" on someone else's personal network, without their explicit permission, irregardless of whether they have it secured or not, is illegal.

However public wifi if I also recall correctly does not bear this ruling, as it is made publicly available. For example, at my college we have an "Open" network, which has no security for guests (Why the fuck can they not just make a secured version of this network that everyone uses the same passkey on instead, will forever elude me.)

We as students are encouraged, literally to the point of which we feel required to not use this network and use our own secured "Student" network, to which we all have our own logins and passwords (Not WPA keys, not WEP, actual login credentials, and they work with all OS's)

Course anyone who doesn't secure their Wireless network provided that they can/have the ability to/should due to various reasons, but leaves it unencrypted for so called "convenience purposes" is foolish in my eyes and mind. I mean sure if you have an old grandma and she has an unsecured wireless router and she doesn't know how to configure it, that's fine but you really should either A. Show her, or B. Configure it and her devices accordingly.

Linux, Winderz, Mac OSX, iWhatever, most all Operating Systems and various devices that support Wifi can store the connection information for respective routers/access points/whatever, 90% of the time in an encrypted form. Additionally using the "connect automatically" feature in each of said OS allows you to..oh shocker..connect without having to retype the password.

It infuriates me when I see an AP that hasn't been secured and isn't belonging to some coffee shop or whatnot.